The invention disclosed in Japanese laid-open patent publication No. 8-304751 is concerned with a projector carrying an imaging device and having an electronic blackboard function to capture an image projected on a projection surface and also to capture graphic figures and characters drawn on the projected image. According to the disclosed invention, a liquid crystal projector for projecting an image onto a screen has a semi-reflecting mirror disposed between a transmissive liquid crystal display panel and a projection optical lens system. The semi-reflecting mirror reflects an image reflected from the screen in a direction other than the transmissive liquid crystal display panel, and the reflected light is captured and converted into a signal by an imaging means.
However, since conventional projectors employ a semi-reflecting mirror, the luminance of the projected image is low. Furthermore, the projector does not have a function, which is sought after by customers in recent years, to project an image obliquely onto the screen and to correct a trapezoidal distortion produced on the projected image.
In order not to sacrifice the projection illuminance, it is necessary to juxtapose the imaging means in the vicinity of the projection lens. There is a commercially available projector which has an imaging device disposed in juxtaposed relation to a projection lens. On such a projector, the imaging device is installed for the purpose of performing such functions as automatic focusing and automatic color correction, not for the purpose of capturing imaging the projected image in its entirety. Therefore, the projector is not used as an electronic blackboard. Though the imaging device which is needed to perform an electronic blackboard function is disposed near the projection lens, it does not have an electronic blackboard function because when the distortion of an image that is projected obliquely onto the screen is corrected, the imaging device would directly capture the distortion-corrected image.